a1 Sandia National Laboratories, Albuquerque, New Mexico 87185, U.S.A.
Tokamak equilibria are considered as extremum magnetic-energy states. Two quadratic invariants ∫Ψd3x, and ∫A.Bd3x are found to yield finite-beta equilibria in toroidal geometry. The theory predicts ‘bell’-shaped current profiles for relaxed discharges at finite beta. A ‘main-sequence’ curve of ql/q0 versus βp is presented for circular discharges with low ql and is found to form a limiting curve for experimental data.
(Received September 29 1989)
p1 Present address: Mission Research Corporation, 8560 Cinderbed Road, Suite 700, Newington, Virginia 22122, U.S.A.